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Which processes are listening on a specific port (e.g. port 80)
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

Remove invalid key from the known_hosts file for the IP address of a host
Quick shortcut if you know the hostname and want to save yourself one step for looking up the IP address separately.

Selecting a random file/folder of a folder
I used only shuf command.

calulate established tcp connection of local machine
If you want prepend/append text just wrap in echo: $echo Connected: `netstat -an|grep -ci "tcp.*established"`

Use colordiff in side-by-side mode, and with automatic column widths.
Barely worth posting because it is so simple, but I use it literally all the time. I was always frustrated by the limitations that a non-gui environment imposes on diff'ing files. This fixes some of those limitations by colourising the output (you'll have to install colordiff, but it is just a wrapper for diff itself), using side-by-side mode for clearer presentation, and of course, the -W parameter, using tput to automatically insert you terminal width. Note that the double quotes aren't necessary if typed into terminal as-is. I included them for safety sake,

Scan for [samba|lanman] NetBIOS names and ip addresses in LAN by ARP.

Show Shared Library Mappings
shows which shared lib files are pointed to by the dynamic linker.

Duplicating service runlevel configurations from one server to another.
And then to complete the task: Go to target host; $ssh host Turn everything off: $for i in `chkconfig --list | fgrep :on | awk '{print $1}'` ; do chkconfig --level 12345 $i off; done Create duplicate config: $while read line; do chkconfig --level $line on; done < foo

Record audio and video from webcam using ffmpeg
Record from a webcam, audio using ALSA encoded as MP3, video as MPEG-4.

Get your outgoing IP address


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